Garfinkel’s breaching experiments are designed to test the reactions of other people to oneself. Garfinkel comes out of the tradition of Ethnomethodology, which studies the understanding of how people understand their social world. Examples of breaching experiments in the modern world (besides ours) are flash mobs or people standing backwards in an elevator. If someone intentionally breaks a social norm for the sake of research, it is considered a breaching experiment. Garfinkel thought that we can break the rules in order to learn the rules.
A breaching experiment is the examination of the reaction caused by someone who breaks the social norms or rule. Thanks to Garfinkel studies like this are available. From what I experienced can be used to learn a lot about how society works.